Combination propellant system using nitrous oxide



P 19, 1967 R. c. WEBSTER ETAL 3,342,672

COMBINATION PROPELLANT SYSTEM USING NITROUS OXIDE Filed May '7, 1964 VACUUM PUMP MACH/IVE.

F/LL ING SA TURA TOP PoPoPr/o/vAL PUMP INVENTORS ROBERT C. WEBSTER JOHN S. /N/\/ PATR/C/A A. LVCHALK ATTORNEY PRODUCT United States Patent 3,342,672 COMBINATIQN PROPELLANT SYSTEM USING NITROUS OXIDE Robert C. Webster, Madison, Wis., John S. Hinn, Minneapolis, Minn., and Patricia A. Lychalk, Des Plaines, 111., assignors to Air Reduction Company, Incorporated,

New York, N.Y., a corporation of New York Filed May 7, 1964, Ser. No. 365,609

6 Claims. (Cl. 16739) This invention relates to the low-cost production of an aerosol spray, the particle size of which is of such maximum diameter that the spray will remain suspended in the air rather than depositing itself on a surface.

More particularly, this invention relates to the commercial production of a propellant and product blend for production of an aerosol spray, of either true aerosol or pressurized spray type, which propellant is reduced in fluorocarbon content.

This invention further relates to the production of a low-cost, nonflammable aerosol mixture of propellant and product of the true aerosol or pressurized spray classification, capable of performance similar to present industrial products.

True aerosol spray and pressurized spray propellant mixtures are used to introduce products, for example various solvents and active ingredients, into the atmosphere, such as insecticides. In order for said products to be effective they must have been broken down to a particle size small enough that they stay suspended in air. This requirement of suspension in the air is as compared to residual sprays in which the particle size is over some minimum size so that the particles deposit on a surface rather than staying in suspension, such as is the case of furniture polish.

It has been a continued area of research in the true aerosol and pressurized spray field to produce a more economical aerosol spray, of the true aerosol or pressurized spray type. Since the advent of the first aerosol spray, for example in the insecticide field, extensive development work has been conducted in a search for new propellants and propellant blends for aerosol products. One of the requirements in this search for new propellants is that the total cost be reduced, without sacrificing desirable product performance characteristics.

An early example of an aerosol insecticide in which the particle size of the product when dispensed in the air 'is smaller than a maximum limit to be defined with more particularity later is disclosed by US. Patent No. 2,321,- 023. The system of this patent consists of using a high pressure container and straight Propellant l2 (dichlorodifluoromethaney The use of liquid carbon dioxide as the propellant is also mentioned. Studies have been made to evaluate the possibility of replacing Propellant 12 in aerosol sprays. One such study is found in the article, Dispersants for Aerosols, by L. D. Goodhue, J. H. Fales, and E. R. McGovern, found in Soap and Sanitary Chemicals 21, vol. 4, pp. 123427, 1945. Systems evaluated were butane, propane, dimethyl ether, methyl chloride and methylene chloride in combination with Propellant 12. The use of compressed gases in the liquid state were also evaluated in 1945, but they did not prove satisfactory, since the dispenser utilized could not withstand the pressure necessary to maintain the compressed gases as a liquid.

Later evaluations also sought the replacement of Propellant 12. An example of such evaluation was published in Industrial and Engineering Chemistry 40, p. 699, 1948, under the title, Propellants for Low Pressure Liquefied Gas Aerosols, by R. A. Fulton. However, such evaluations did not disclose the substitution for a part of the fluorocarbon propellant with nitrous oxide or carbon dioxide for economy and other reasons and the addition of low-cost solvent with essentially no vapor pressure to boost solubility and maintain the proper product characteristics.

When low pressure aerosols were officially introduced to the public, a combination of Propellant 11 (trichloro fiuoromethane) and Propellant 12 was used. Propellant 114 (sym-dichlorotetrafluoromethane) was later substituted for Propellant 11 in some cases. In 1956, W. H. Reed suggested in Soap and Chemical Spec. 32 (5) 197, in an article entitled A New Propellant Blend that isobutane be combined with Propellants 11 and 12 in the propellant system. (Other blends have been suggested and are in use, such as a blend consisting of butane and Propellant 12, dimethyl ether and Propellant l2, and vinyl chloride and Propellant 12.)

As can be seen from the brief description of the history of aerosol sprays contained above, many solvent systems as well as other liquefied gases have been proposed and evaluated. However, the most feasible blends developed up to the time of this invention still rely upon fluorocarbons to supply pressure to dispense and break up the solvent.

There are many factors that have to be taken into consideration when propellant and product blends are developed. The main considerations, however, in the development of a propellant system are:

(1) A system which will yield the desired performance characteristics;

(2) A nonfiammable system; and

(3) A low cost or less expensive system than the known propellant systems.

It is an object of this invention to produce a true aerosol or pressurized spray of'substantially as high or higher performance characteristics and lower cost than those true aerosol or pressurized sprays presently produced.

It is further an object of this invention to produce a low-cost true aerosol or pressurized spray which is nonflammable.

It is further an object of this invention to produce a spray which has a particle size so as to remain suspended in the air when dispensed, said spray being of relatively low cost when compared to the sprays of the same type presently being produced.

In producing an aerosol spray of the pressurized spray or true aerosol spray type, defined with particularity below, the particle size is of utmost concern. In general, the size depends upon the pressure in the package and the volume ratio of propellant to concentrate. If the volume of liquefied propellant is decreased, the resultant particles will become larger; however, if the pressure is increased, a finer spray is usually obtained.

Insecticides and room deodorants are examples of commercial products that would normally fall into a pressurized spray or true aerosol spray classification.

The spray from a true aerosol dispenser should be in a finely divided form in which eighty percent or more of the individual spray particles have a mean diameter of 30 microns or less and none of the spray particles has a diameter of more than 50 microns.

Pressurized sprays are products that deliver sprays which remain suspended in the air but do not meet the true aerosol requirements.

Aerosol sprays of the pressurized and true aerosol spray types are differentiated from residual sprays in which the particles deposit on a surface rather than staying in suspension in the air. This invention is conthey will remain suspended in the airis not encountered in the residual spray.

Generally, in order to achieve a true aerosol or pressurized spray, 80 to 85 percent of the total package ingredients should be propellant gas. The propellant gas has in the past been made up largely of Propellants 11 and 12. Propellant 11 is less expensive than Propellant 12 and has been used with Propellant 12 in order to reduce the cost. In addition, Propellant 11 serves to modify the pressure.

It is Propellants 11 and 12, along with the valve arrangement utilized, which break up the solvent upon emission from the aerosol container. It is the proposal of this invention to reduce the amount of propellant in the form of fluorocarbon and boost the pressure with compressed gas in the form of either nitrous oxide or carbon dioxide, thus dramatically reducing the cost of the aerosol spray while maintaining substantially as good or better quality characteristics. In order to achieve proper break up and dispensing of the solvent, the reduction in the percentage of propellant fluorocarbon (P-11 and P12) and the substitution therefor with nitrous oxide or carbon dioxide, requires that a satisfactory auxiliary solvent be added so that the total inactive contents of the aerosol package remains in the range of 80 to 85 percent. Chlorothene, methyl chloroform (1,1,1-trichloroethane) is an example of such a satisfactory auxiliary solvent since it is nonflammable, non-toxic, non-irritating, odorless, possesses high solubility for gaseous nitrous oxide or carbon dioxide, has a low hydrolization return, and has a specific gravity comparable to P11 and P-12. Its good solvency is of great importance, since the boosted solubility allows for the effectiveness of the formulation with reduced fluorocarbon propellant and substituted nitrous oxide or carbon dioxide. Furthermore, Chlorothene essentially has no vapor pressure itself which is of great advantage in the pressurized system in which it is utilized.

Nitrous oxide gas presents an excellent medium for boosting the pressure within the aerosol container, since it is nonflammable, non-toxic, and non-irritating and under atmospheric conditions exists in a gaseous state. In addition nitrous oxide is soluble in both water and other solvent systems. As previously mentioned, carbon dioxide may also be utilized. The use of compressed nitrous oxide gas is preferable to the use of compressed carbon dioxide gas, since it (N has a higher solubility allowing more nitrous oxide gas propellant per unit volume of solution as compared to carbon dioxide and thus provides greater assurance of proper dispensing and break up of product. Furthermore, since carbon dioxide tends to carbonate water (and the precipitation of product ingredients) with the resulting formation of carbonic acid which corrodes the dispenser can, the use of nitrous oxide is preferable wherever a water solution is a possibility.

The compressed nitrous oxide (or carbon dioxide) gas acts as an energy source and atomizing agent in the propulsion of aerosol products from a container to form a true aerosol or pressurized spray. It is to be noted that the fluorocarbons must still be present in the container in order that the flashing of liquid propellant to gas at the orifice may take place and in order that the particle size of the solvent be broken down sufliciently so as to create a true aerosol of pressurized spray. The reduction of the fluorocarbon requirements within the true aerosol or pressurized container results in a reduction of cost, without damaging sacrifice of quality product spray. It has been discovered that such reduction of fluorocarbon requirements is made possible with the introduction of nitrous oxide or carbon dioxide compressed gas, preferably nitrous oxide compressed gas as discussed above, into the container to boost the pressure. The addition of nitrous oxide (or carbon dioxide) compressed gas to a container as a substitute for part of a fluorocarbon propellant in order to boost pressure for the dispensing of a true aerosol or residual spray with a dramatic reduction of cost, while not sacrificing performance characteristics, is thus the subject matter of this invention.

The compressed gas used should be suflicient to produce equilibrium pressures to the maximum allowable limit of the containers used, usually to 100 p.s.i.g.

The use of a propellant system comprised of fluorocarbons, nitrous oxide (or carbon dioxide) compressed gas and an auxiliary solvent such as Chlorothene results in a reduced propellant cost as compared to the cost of fluorinated hydrocarbons as the sole propellant, results in a nonflammable system as compared to the use of fluorinated hydrocarbons or hydrocarbon blends, results in a minimal pressure drop over the use life of the container as compared to using nitrous oxide or carbon dioxide as the sole propellant, with much more satisfactory particle size consistency, and results in a maintenance of the desired particle size so that the spray may remain suspended in the air as required in the true aerosol sprays or pressurized spray requirements.

The subject matter of this invention will now be discussed in more detail in relation to a particular aerosol spray. It is emphasized at the outset that the particular aerosol spray discussed below is merely exemplary of any of a number of sprays of the true aerosol or pressurized type which may be introduced into the air to remain suspended therein.

One particular form of pressurized insecticide is formed with the following ingredients, according to this invention:

TABLE I Percent Ingredients: by weight MKG Pyrocide Aerosol Mix 933 20.0

Pyrethrins (0.30). MGK 264 (1.00). Piperonyl butoxide (0.60). Petroleum distillate (18.10). Chlorothene 55.0

Propellant Propellant 12 (dichlorodifluoromethane) 25.0 Nitrous oxide-compressed gas to p.s.i.g.

equilibrium.

In the commercial packaging of the formulation of Table I the percentage by weight of nitrous oxide compressed gas (or carbon dioxide) should be subtracted from the Chlorothene portion of the ingredient. This establishes the correct formula, total ingredients adding to percent.

As previously discussed, the nitrous oxide compressed gas (or carbon dioxide) is used to boost the pressure within the aerosol container so that the amount of propellant (in this case, Propellant 12) may be reduced. As stated earlier and discussed in detail, the addition of Chlorothene is of vital importance to the proper dispensing of the propellant and solvent formulation according to this invention as, for example, the formulation of Table I.

The particle size upon dispensing of the formulation of Table I, when sprayed into the atmosphere with a particular commercial spray type brand valve (a Precision valve) with a mechanical breakup actuator was distributed from 3 microns to 79 microns at 100 cumulative weight percent. The mean particle size was 24 microns. Since the specific requirement is for a true aerosol to have no particles of a diameter more than 50 microns, the particular formula spray disclosed above, when used with the particular valve discussed, would be classified as a pressurized spray. However, whether pressurized or true aerosol, the significant fact is that the spray particle size is such that the spray remained suspended in the air when dispensed.

Table II reproduced below indicates that the pres surized insecticide noted in Table I will perform in a manner similar to or better than the official aerosol test sample (OTA), which utilized about 80 percent straight fluorocarbon propellant and a pyrethrin active ingredient formula, as in Table I. A-29l7 formulation noted in Table II is the formulation recorded above in Table I.

As stated earlier in this specification, one of the major factors in the development of the propellant system of this invention is its relative low cost. The table following demonstrates said relatively low cost. As is readily ap- TABLE II Dosage, Knockdown (min) Knock- Sample Valve gin/1,000 down cu. ft. Mor- 5 10 tality 3. 05 31 55 93 87 3. 10 22 35 72 71 0. 05 +9 +21 +16 2.92 37 69 87 76 3. 14 29 53 68 67 -0. 22 +6 +16 +19 +9 11-2917 N ewman- Green. 2. 86 24 46 90 80 0 TA 3. 10 22 35 72 71 KTA Diff 0. 24 +2 +11 +18 +9 (3 oz. avoir.).

3 Evaluated when container at one hundred percent full level (12 oz. avoin}.

It should be noted that the aerosol spray utilizing nitrous oxide (or carbon dioxide) compressed gas partially in place of fluorocarbon propellant, as for example, the pressurized insecticide of Table I, remains stable for long periods of time, in nonflamrnable, and does not suffer any particularly destrimental pressure drop when compared to test samples using only fluorocarbon propellant. It might be pointed out that where the chemical formulation noted in Table I is compared to an ofiicial test aerosol pressurized insecticide using a combination of Propellant 11 and Propellant 12, without nitrous oxide or carbon dioxide, the pressurized insecticide of Table I is as eifectiveor more effective than the OTA sample using Pl1 and P-12 as the propellant system, as shown in Table III.

TABLE III Knockdown (min) Sample Dosage, Knockdown gun/1,000 Mortality cu. ft. 5 10 15 Another specific example of an aerosol spray of this invention is an aerosol deodorant composed of the components listed in Table IV below. Said aerosol deodorant was tested for particle size. The following chart compares the particle size of two components in which carbon dioxide was substituted for Propellant 12 in the manner discussed above. Sample 1 was the control sample,

utilizing a high percentage of Propellant 12 as the sole propellant. In samples 2 and 3 carbon dioxide was added to an equilibrium of 85 p.s.i.g. The carbon dioxide content of sample 2 was 4.3 grams and of sample 3 was 4.1 grams. The particle size remains small enough upon dispersion for samples 2 and 3 so that the deodorant would remain suspended in the air.

5 parent the cost per 100 cans is appreciably reduced when using the formula, including nitrous oxide, in substitution for a part of the fluorocarbon propellant.

TABLE V Ingredient B y Wt. Unit #IM $/M (Percent) Cost/i? 1 Cans 2 Cans Formula No. l:

933 3 20 1. 21 149. 60 181.01 P-ll- 40 0. 22 299. 20 65. 82 P-12 40 O. 26 299. 20 77. 79

Total 324. 62 Per Cau 0.324

Total 287. 58

Per Can 0.287

1 Prices Approximate.

2 Cost figures calculated on the basis of a 12 oz. avoir. fill in a 12 oz. container.

3 McLaughlin Gormley King Company Pyrocide Mix 933.

4 Percent of Chlorothene reduced to accommodate Nitrous Oxide.

1 product, fluorocarbon propellant, Chlorothene, and nitrous oxide (or carbon dioxide) compressed gas, and that the invention is not limited to said one specific way. Furthermore, the invention is not limited to any particular manner of filling an aerosol dispenser.

The drawing shows, in schematic fashion, the process for filling a dispenser with an aerosol filler including nitrous oxide compressed gas and Propellant 12.

The product (solvent) is stored in chamber 1 for introduction through pump apparatus 2 to a saturator 3. The product in the case of the insecticide of Table I includes the Chlorothene necessary. The propellant is stored in container 4 for introduction into the saturator 3 through valve 5. The propellant in the case of the formulation of Table I is Propellant 12 (di-chlorodifiuoromethane). It is contemplated that the propellant and the product will be intermixed before introduction into the saturator 3 and will pass into the saturator through spray device 6. Com pressed gas, that is nitrous oxide, will be passed through the combined product and propellant in the saturator so as to boost the pressure therein. The compressed gas as shown is stored in a gas cylinder 7 to be conducted through line 8 to the saturator 3. In the saturator the aerosol mixture is boosted in pressure as a result of being gasified by the compressed gas. The high pressure mixture of propellant, nitrous oxide, Chlorothene and product is then pumped by a pump mechanism 9 to a filling machine 10 where it is introduced into aerosol dispensers. Said filling operation is implemented by the creation of a partial vacuum within the individual dispensers, created therein by a vacuum pump 11. The dispenser thus has therein the particular product (solvent), Chlorothene, the fluorocarbon propellant necessary for properly breaking down the particle size so that the particle of solvent will remain suspended in the air upon being dispersed, and the compressed nitrous oxide which boosts the pressure within the container, replacing a part of the fluorocarbon propellant at a lower cost with substantially the same or better quality.

The dispenser will normally be valved so that dispensing of the product will result in breakup at the point of the valve upon dispensing of the product into small particles for suspension in the air. The propellant (in the formulas of Table I, dichlorodifluoromethane) is the driving force that causes the product to break into small particles upon release from the pressurized container into the atmosphere at the point of the valve.

The dispenser may be filled in a variety of alternate manners. One such other alternate manner of filling is to introduce the product (solvent) and Chlorothene into the empty container, followed by adding the fluorocarbon propellant to the container by pressure filling after purging of the container with the propellant to be used. At this point in the filling operation the aerosol package contains concentrated fluorocarbon and product. The dispenser is now ready to receive the compressed gas which is introduced while the container is being agitated, perhaps by a gasser-shaker.

A number of different alternative methods for filling dispensers with the ingredients of the aerosol package may be used. Two filling operations have been set forth above; however, this invention is not to be limited by any particular filling method; rather, the two methods outlined above are included in this disclosure for purposes of example.

The inventors are aware of the fact that nitrous oxide, and carbon dioxide, have been used before in an aerosol package, for example, in residual aerosol sprays as a propellant alone or incombination with other propellants. However, the inventors have developed a novel and useful approach to the handicapping cost problem of the use of fluorocarbon propellants, for example, Propellant 11 and Propellant 12, or a combination thereof, in true aerosol and pressurized spray systems. As discussed hereinbefore, this invention particularly relates to the use of com-pressed gaseous nitrous oxide or carbon dioxide to boost the pressure in an aerosol container and thus allow less fluorocarbon propellant to be used, with the addition of Chlorothene, while maintaining a breakup of particle size sufficient that the spray will remain in the air. This invention, as set forth above, is a novel and highly useful manner of reducing the cost of the true or pressurized aerosol sprays, while substantially maintaining the breakup qualities of the propellant on the solvent and while substantially maintaining or bettering the quality of the product.

It is also recognized by the inventors that proposals have been made to choose a particular solvent in which nitrous oxide or carbon dioxide may be dissolved so that the use of fluorinated hydrocarbons can be eliminated. This invention, however, deals with the substitution for a part of the fluorinated hydrocarbon with nitrous oxide and/or carbon dioxide compressed gas and the addition of Chlorothene to boost solubility, improve performance characteristics, without adding essentially any vapor pressure of is own. It is emphasized that the remaining fluorinated hydrocarbon still provides the force for breaking up the liquid into small enough particles to remain suspended in the air, resulting in a high quality aerosol spray of either the true aerosol or pressurized spray type. Furthermore, the elimination of fluorinated hydrocarbons as the propellant with the attendant problems of the high solubility needed and lack of proper breakup of solvents are avoided.

The scope of our invention should not be limited by any of the specific examples of true aerosol spray or pressurized spray disclosed above or any particular method of filling an aerosol package disclosed above but rather only by the following claims.

We claim:

1. A pressurized dispenser comprising a container and a non-aqueous composition therein said composition consisting essentially of (l) more than about half by weight of methyl chloroform, (2) the product to be dispensed in the form of particles which will substantially remain in the atmosphere without settling out of said atmosphere and (3) dichlorodifluoromethane for breaking up said product into said particles upon dispensing, and nitrous oxide compressed gas added to the composition within the container to effect an equilibrium pressure within the container of up to about 100 psi. g.

2. A pressurized dispenser comprising a container and a non-aqueous composition therein said composition consisting essentially of (1) more than about half by weight of methyl chloroform, (2) the product to be dispensed in the form of particles which will substantially remain in the atmosphere without settling out of said atmosphere and (3) dichlorodifluoromethane and t richlorofiuoromethane for breaking up said product into said particles upon dispensing, and nitrous oxide compressed gas added to the composition within the container to effect an equilibrium pressure within the container of up to about 100 p.s.i.g.

3. A pressurized dispenser comprising a container and a non-aqueous composition therein said composition consisting essentially of about 20% by weight of the product to be dispensed in the form of particles which will substantially remain in the atmosphere without settling out of said atmosphere, about 55% by weight of methyl chloroform, about 25% by weight of dichlorodifluoromethane for breaking up said product into said particles upon dispensing, and nitrous oxide compressed gas added to the composition within the container to effect an equilibrium pressure within the container of up to about 100 p.s.i.g.

4. A pressurized dispenser as claimed in claim 3, the nitrous oxide compressed gas added to the solution to a pressure of about p.s.i.g. equilibrium.

5. A pressurized dispenser comprising a container and a non-aqueous composition therein said composition consisting essentially of (1) a substantial percentage by weight of methyl chloroform, (2) the product to be dispensed in the form of particles which will substantially remain in the atmosphere without settling out of said atmosphere and (3) dichlorodifluoromethane for breaking up said product into said particles upon dispensing, and nitrous oxide compressed gas added to the composition within the container to effect an equilibrium pressure within the container of up to about p.s.i.g.

6. A pressurized dispenser comprising a container and a non-aqueous composition therein said composition consisting essentially of (l) a substantial percentage by weight of methyl chloroform, (2) the product to be dispensed in the form of particles which will substantially remain in the atmosphere without settling out of said atmosphere and (3) dichlorodifluoromethane and trichlorofluoromethane for breaking up said product into said particles upon dispensing, and nitrous oxide compressed gas added to the composition within the container to effect an 100 p.s.i.g.

References Cited UNITED STATES PATENTS Iddings 167-39 5 Reasen'berg 167--39 Efford 167-39 Riley 167-39 1 0 OTHER REFERENCES Aerosol Age, v01. 8, No. 6, pp. 29 and 75, June 1963. Barber: Chlorothene in Aerosols, Soap and Chem. Engr., vol. 33, No. 2, pp. 99, 103, 105, and 209 (1957).

ALBERT T. MEYERS, Primary Examiner. J. D. GOLDBERG, Assistant Examiner. 

3. A PRESSURIZED DISPENSER COMPRISING A CONTAINER AND A NON-AQUEOUS COMPOSITION THEREIN SAID COMPOSITION CONSISTING ESSENTIALY F ABOUT 20% BY WEIGHT OF THE PRODUCT TO BE DISPENSED IN THE FORM OF PARTICLES WHICH WILL SUBSTANTIALLY REMAIN IN THE ATMOSPHERE WITHOUT SETTLING OUT OF SAID ATMOSPHERE, ABOUT 55% BY WEIGHT OF METHYL CHLOROFORM, ABOUT 25% BY WEIGHT OF ICHLORODIFLUOROMETHANE FOR BREAKING UP SAID PRODUCT INTO SAID PARTICLES UPON DISPENSING, AND NITROUS OXIDE COMPRESSED GAS ADDED TO THE COMPOSITION WITHIN THE CONTAINER TO EFFECT AN EQUILIBRIUM PRESSURE WITHIN THE CONTAINER OF UP TO ABOUT 100 P.S.I.G. 